The goal of this proposal is to study the function of PYRIN domain containing proteins in innate immune responses following pathogen infection. Several pathogen recognition receptors are composed of a PYRIN domain, a central nucleotide binding NACHT domain and a leucine rich region. While the leucine rich region functions as pathogen receptor, the PYRIN domain recruits PYRIN domain containing adaptor proteins, such as ASC. Recruitment of ASC links pathogen recognition to the activation of downstream effector pathways of the innate immune system. Known effectors include activation of caspase-1 and NF-?B, as well as induction of MHC class 1 expression, which is crucial for host cell defense. Impaired regulation of this pathway is also linked to several autoinflammatory disorders. Our preliminary results suggest that signals transmitted by the PYRIN domain are not limited to these effectors, but can also activate stress-induced signal transduction pathways, which may support pathogen clearance. In particular we found that expression of the central adaptor protein ASC which contains a PYRIN domain and links signals from pathogen recognition receptors to downstream effector pathways, can induce Jun-N-terminal kinase (JNK) activation and subsequently promotes cell migration. We propose to employ THP-1 monocytes that can be differentiated into adherent macrophages and analyze PYRIN domain mediated signaling pathways. PYRIN domain signaling will be induced by employing defined ligands for the PYRIN domain containing pathogen recognition receptors. We generated ASC expressing stable THP-1 cell lines that mimic pro-inflammatory mediator-induced upregulation of the ASC protein. Cell lines with silenced ASC expression will help to associate downstream signalling events specifically with the PYRIN domain mediated signal transduction pathway. This proposal seeks to define a novel signal transduction pathway of PYRIN domain containing proteins, which is relevant for pathogen recognition and innate immune regulation. This research is also significant for several autoinflammatory disorders that are linked to hereditary mutations in genes encoding PYRIN domain containing pathogen recognition receptors. The here proposed work extends our long-term goal to define the mechanisms that link pathogen recognition to the innate immune response. [unreadable] [unreadable] [unreadable]